Process for making electrolytic iron



Fei. Il, 1930. R. D. PIKE- PROCESS FOR MAKING ELECTROLYTI IRQN Filed Jan. -4. 1926 HNFJ man wmwf @2E/Dm :D O

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Patented Fel?. l1, 1930 ROBERT D. PIKE, OF'PIEDMONT, CALIFORNIA- PROCESS FOR lVIAKIN G ELECTROLYTIC IRON Application led January 4, 1926. Serial No. 79,061.

In my application for United States Patent, Serial Number 58,012, l describe a process for making electrolytic iron from lsulphide ores as a. by-product of ai process for recovering the more valuable metals of such ores. As pointed out therein, it is preferable to use chloride solutions in such a process; and when ferrous chloride is usedas electrolyte in the diaphragm iron'cell it is necessary to ca-rry temperatures 70o C. or higher, to havc satisfactory .,deposits.

My "present invention covers a process for making`V pui'e'electrolytic iron as a main product starting with sponge iron as araw material Lvandemployingr a ferrie chloride leach and a ferrous chloride electrolyte for the diaphragm iron cell. In carrying out my process I preferably employ as raw material the sponge iron now being manufactured and known to metallurgists as Chino sponge iron. Chino iron is a special product made by the Chino Copper Company. by the socalled Thornhill and Anderson process. Its special property is that it is very finely divided and highly reactive in a chemical sense. I have discovered that when this iron is added to a leach liquor containing' 8% to 10% total iron 'as chloride, about one-half as ferrie and one-half as ferrous, a violent. reaction occurs, whereby the iron of the sponge iron Iloes into solution as ferrous chloride. thereby completely reducing the ferrie chloride of the leach liquor, and the temperature of the This liquor is then treated to the. necessary puriication steps as rapidly as possible and transferred to the iron cell Where its elevated teml:eraturtnprincipally derived from the sponge iron reaction, reduces or entirely eliminates the steam-heating required to maintain the temperature of the iron cell. This is of particular importance when using the cells described in my application for United States Patent, Serial Number 58,000, filed September 23. 1925, and in the application by myself and Messrs. Little and ll'vest. Serial Number 58,010, filed September 23. 1925. in which the a hot electrolyte, i. e., 90 C. to 100 C., into the cell. y

The electrolyte is purified as described in my above-mentioned applications, and a certain amount is bled7 at each cycle, depending upon the impurities in the sponge iron, but usually about 3% of the total amount in circulation. This amount -is then treated with milk of lime to precipitate Mg', Al. and Fe and to make CaCL. This latter is then treated with ferrous or ferrie sulphate, making the corresponding chlorides ot' iron and precipitating` gypsum. `he regenerated iron chlorides are returned to thc circuit.

By means of my process I am enabled to -start with a sponge iron containing 80% of metallic iron, more or less, and to directly produce a practically chemically pure iron.

A more detailed idea of a specific application of my process may be had by reference to the accompanying drawing. wherein the figure shows a fiow sheet. There may be considerable departure from the details-of this flow sheet within the meaning of my invention.

In the dra wing I show a leach tank l, preferably made o. concrete, with propeller agitator l". preferably covered with rubber. Anolyte leach returningr from the electrolytic iron cells enters this tank in a continuous stream and is mixed with a stream of sponge iron introduced by a mechanical feeder. not. shown. The sponge iron is introduced in slight excess so that the ferrie iron will be completely' reduced. and any copper or other relatively electro-meative metals. such as lead. will remain with the solids in tank l.

"he overflow from tank 1. containing all undissolved solids. goes to thickener the underflow of which Agoes to filter The clear liquor from 3 may directly join the clear overflow from the thickener` but I vhave discovered that when copper is present. in even small amounts. in the solids. and such solids are filtered from the liquors, which are high in iron. a small amount of oxidation ofthe latter will always occur during filtering'. forming traces of ferrie chloride. and this ferrie chloride will attack and redissolve some of the copper in the press cake even when the latter contains a surplus of met-allic iron. On this account, the clear liquor from the press will contain traces of copper. .From the standpoint of copper recovery, these amounts are small and could be neglected commercially, but they are sufficient to cause serious copper contamination of the electrolytic iron. For example, it is desirable that the latter contain not more than .Ulf/7` Cu and preferably less, it the highest electromagnetic properties are to be realized. But I have found that in usual practice forty pounds of fresh electrolyte are supplied to the iron cell for each pound of iron produced, and that most of the copper in this electrolyte plates out with the iron. On this account the electrolyte should contain, as a maximum, .000570 of Cu. There is no difi'iculty in obtaining a copper-free overflow Jfrom the thickener Q, but the clear liquor from the filter 3 should be returned to the tank 1 for reprecipitation of its contained copper. The separation on a conunerc'ral reale of copper-free solutions ot' ferrous chloride from .solids containing copper is a novel and important feature of my invention.` rl`l1e overflow yfrom the thickener 2 goes to gastreating tower 4, where it is treated with ILS gas for precipitation of the Zn and other metals or sulphides which may remain after the treatment in tank 1. In usual practice these other metals only occur in traces, if at all. The underflow from gas-treating tower l goes to thickener The underflow from thickener 5 is filtered in filter 6, the clear liquor from which joins the overflow from thickener 5. Any traces of copper in the liquor entering the gas-treating tower il would presumably be precipitated by HZS, but the same slight oxidation and resolution of sulphides in filter 6 would'occur as in filter 3, so it 1s liest to assure complete removal of copper by returning `the clear liquor from filter 3 to tank 1. The purified liquors can now go through an evaporator 7, if necessary, lout because of' the great amount of heat generated in the reactionin tank 1, but little live steam is introduced in the cycle for heating, so that in practice evaporation is usually found to be unnecessary. V

rl'he bled portionof the electolyte goes to agitator 8, where sufiicient milk of lime is added to precipitate all Fe, Mg, and Al present as hydrates, and the resulting CaCl2 solution is filtered clear at 9.. -The CaCl2 goes to an agitator 10, where it is mixed wit-hierrous or ferrie sulphate. If this latter is used it may be made by treating some readily solu-v ble form of iron oxide with sulphuric acid in 11, and then adding to agitator 10 with or without filtration. The overflow from agitator 1f) is filtered at filter 12 and the clear i liquor goes hack to tank 1. A

The purified electrolyte, after removal of the bled portion, goes to electrolyte storage storage tank 13. Live steam may be intro' duced at the latter point to make up for heat losses in the cycle.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

l. In a cyclic process for the production of substantially copper-free electrolytic iron from solutions containing copper, the steps for removal of the copper from the solutions which consist of treating the copper-bearing solutions with metallic iron, the removal of the main portion of the copper-free liquor from the precipitated copper by decantation, the filtering of the cement copper, and the return ot the filtered liquor for reprecipitation ofits copper content on iron.

Q. In a cyclic process for the production of substantially copper-free electrolytic iron from solids containing copper, which consists of adding sponge iron to a leach containing iron chloride in a precipitating tank, passing the overfiow solution from said tank to a thickener,f returning the underflow from the thickener to the.precipitatingtank for reprecipitation ofelectro-negative metals, sub. 

